The battery, which comes in two models, a 10kWh capacity and a 7kWh capacity, is designed to be a backup power source for people’s homes. The wall-mounted battery works by absorbing solar energy from exterior panels and storing that energy for later use, such as when a residence’s traditional power sources experience a blackout. The battery first went on sale last May and sells for $3,750 or $3,000 depending on the capacity. All units of the Powerwall sold out within its first 10 days of availability and Tesla soon announced that there was a backlog of orders until 2016.

However, those wanting to get their hands on a Powerwall might do better to wait a few more months. At an event centered around Tesla’s line of automobiles in Paris this week Musk revealed, ”We’ll be coming out with a version two of the Powerwall probably around July or August of this year, which will see a further step change in capabilities.”

What those new capabilities are Musk didn’t reveal. However it is known the Powerwall 2 will use battery cells built by Tesla’s own Gigafactory in Nevada. The battery cells in the first generation Powerwall are made by Panasonic. It’s possible Tesla’s own cells could gather and store more energy or be more efficient at doling it out.

If you want to know more about the current Powerwall and how it works, you can check out Tesla’s promo video below.